diff --git a/CHANGELOG.md b/CHANGELOG.md
index 94900bcb31..eab041079d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,9 +4,15 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## Unreleased
+
+### Added
+
+* Support IDNA2003. (#3229)
+
 ## 0.27.1 (27th August, 2024)
 
-## Added
+### Added
 
 * Support for `zstd` content decoding using the python `zstandard` package is added. Installable using `httpx[zstd]`. (#3139)
 
diff --git a/docs/api.md b/docs/api.md
index d01cc649ba..0c1ae84704 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -126,6 +126,7 @@ what gets sent over the wire.*
 * `.is_ssl` - **bool**
 * `.is_absolute_url` - **bool**
 * `.is_relative_url` - **bool**
+* `.strict_idna` - **bool**
 * `def .copy_with([scheme], [authority], [path], [query], [fragment])` - **URL**
 
 ## `Headers`
diff --git a/httpx/_urlparse.py b/httpx/_urlparse.py
index 479c2ef8a1..17abb58005 100644
--- a/httpx/_urlparse.py
+++ b/httpx/_urlparse.py
@@ -199,6 +199,8 @@ def urlparse(url: str = "", **kwargs: str | None) -> ParseResult:
         if ":" in host and not (host.startswith("[") and host.endswith("]")):
             kwargs["host"] = f"[{host}]"
 
+    strict_idna = bool(kwargs.pop("strict_idna", False))
+
     # If any keyword arguments are provided, ensure they are valid.
     # -------------------------------------------------------------
 
@@ -256,7 +258,7 @@ def urlparse(url: str = "", **kwargs: str | None) -> ParseResult:
     # with components that are plain ASCII bytestrings.
     parsed_scheme: str = scheme.lower()
     parsed_userinfo: str = quote(userinfo, safe=SUB_DELIMS + ":")
-    parsed_host: str = encode_host(host)
+    parsed_host: str = encode_host(host, strict_idna=strict_idna)
     parsed_port: int | None = normalize_port(port, scheme)
 
     has_scheme = parsed_scheme != ""
@@ -300,7 +302,7 @@ def urlparse(url: str = "", **kwargs: str | None) -> ParseResult:
     )
 
 
-def encode_host(host: str) -> str:
+def encode_host(host: str, strict_idna: bool = False) -> str:
     if not host:
         return ""
 
@@ -342,9 +344,15 @@ def encode_host(host: str) -> str:
 
     # IDNA hostnames
     try:
-        return idna.encode(host.lower()).decode("ascii")
+        encoded = idna.encode(host.lower())
     except idna.IDNAError:
-        raise InvalidURL(f"Invalid IDNA hostname: {host!r}")
+        if strict_idna:
+            raise InvalidURL(f"Invalid IDNA hostname: {host!r}")
+        try:
+            encoded = host.lower().encode("idna")
+        except UnicodeError:
+            raise InvalidURL(f"Invalid hostname: {host!r}")
+    return encoded.decode("ascii")
 
 
 def normalize_port(port: str | int | None, scheme: str) -> int | None:
diff --git a/httpx/_urls.py b/httpx/_urls.py
index ec4ea6b399..3230761755 100644
--- a/httpx/_urls.py
+++ b/httpx/_urls.py
@@ -5,6 +5,7 @@
 
 import idna
 
+from ._exceptions import InvalidURL
 from ._types import QueryParamTypes, RawURL
 from ._urlparse import urlencode, urlparse
 from ._utils import primitive_value_to_str
@@ -75,6 +76,7 @@ class URL:
     """
 
     def __init__(self, url: URL | str = "", **kwargs: typing.Any) -> None:
+        self._strict_idna = kwargs.pop("strict_idna", False)
         if kwargs:
             allowed = {
                 "scheme": str,
@@ -114,7 +116,7 @@ def __init__(self, url: URL | str = "", **kwargs: typing.Any) -> None:
                 kwargs["query"] = None if not params else str(QueryParams(params))
 
         if isinstance(url, str):
-            self._uri_reference = urlparse(url, **kwargs)
+            self._uri_reference = urlparse(url, strict_idna=self._strict_idna, **kwargs)
         elif isinstance(url, URL):
             self._uri_reference = url._uri_reference.copy_with(**kwargs)
         else:
@@ -186,9 +188,12 @@ def host(self) -> str:
         assert url.host == "::ffff:192.168.0.1"
         """
         host: str = self._uri_reference.host
-
         if host.startswith("xn--"):
-            host = idna.decode(host)
+            try:
+                host = idna.decode(host)
+            except (idna.IDNAError, idna.core.InvalidCodepoint):
+                if self._strict_idna:
+                    raise InvalidURL(f"Invalid IDNA host: {host!r}")
 
         return host
 
diff --git a/tests/client/test_redirects.py b/tests/client/test_redirects.py
index f65827134c..a0b46d4fea 100644
--- a/tests/client/test_redirects.py
+++ b/tests/client/test_redirects.py
@@ -37,7 +37,7 @@ def redirects(request: httpx.Request) -> httpx.Response:
 
     elif request.url.path == "/invalid_redirect":
         status_code = httpx.codes.SEE_OTHER
-        raw_headers = [(b"location", "https://😇/".encode("utf-8"))]
+        raw_headers = [(b"location", "https://�/".encode("utf-8"))]
         return httpx.Response(status_code, headers=raw_headers)
 
     elif request.url.path == "/no_scheme_redirect":
diff --git a/tests/models/test_url.py b/tests/models/test_url.py
index 523a89bf65..b9e6f0f1d5 100644
--- a/tests/models/test_url.py
+++ b/tests/models/test_url.py
@@ -349,7 +349,16 @@ def test_url_invalid_hostname():
     Ensure that invalid URLs raise an `httpx.InvalidURL` exception.
     """
     with pytest.raises(httpx.InvalidURL):
-        httpx.URL("https://😇/")
+        httpx.URL("https://😇/", strict_idna=True)
+    with pytest.raises(httpx.InvalidURL):
+        assert httpx.URL("https://xn--n3h.com/", strict_idna=True).host
+
+
+def test_url_with_emoji():
+    assert str(httpx.URL("https://😇/")) == "https://xn--l28h/"
+    assert httpx.URL("https://😇/") == httpx.URL("https://xn--l28h/")
+    assert httpx.URL("https://😇/", strict_idna=False) == httpx.URL("https://xn--l28h/")
+    assert str(httpx.URL("https://☃.com/")) == "https://xn--n3h.com/"
 
 
 def test_url_excessively_long_url():
@@ -802,7 +811,7 @@ def test_url_escaped_idna_host():
 
 def test_url_invalid_idna_host():
     with pytest.raises(httpx.InvalidURL) as exc:
-        httpx.URL("https://☃.com/")
+        httpx.URL("https://☃.com/", strict_idna=True)
     assert str(exc.value) == "Invalid IDNA hostname: '☃.com'"